Download THIS FILE[drive.google.com]

Then put the file in the folder:
Steam\SteamApps\common\left 4 dead\left4dead\scripts. Make a backup of the original file, just in case

Then go here:
Steam\SteamApps\common\left 4 dead\left4dead\cfg And create a file autoexec.cfg.
Open this file and enter these lines:

bind "v" "+mouse_menu Vocalize1"
bind "b" "+mouse_menu Vocalize2"
bind "n" "+mouse_menu Vocalize3"
bind "m" "+mouse_menu Vocalize4"

Can bind any other button.

Save the file and close. That's all :)

Watch the video if you see this vocalize command